In casting processes, critical operations are generally related to the molding of the piece and core molding of its components. The latter consists in obtaining plugs (normally made from refractory materials) and their addition to the molds, in order to form cavities, holes and indentations on the pieces.
An internal air circulation system, including cooling ducts inside the engine housing, is necessary for optimal functioning of large and medium-sized rotating electrical machines. Such composition enables the cooling means to effectively remove the heat generated from losses, a parameter that is intimately associated to the useful lifespan of the machine.
In case of engines with cast iron housings, the application of casting plugs is required to obtain such ducts. The main drawbacks regarding core molding are found in the variables introduced in the design specification, such as the possibility of beads and bubble formation due to inadequate gas removal, or in more extreme situations, ejection of liquid metal from within the molds. Another relevant factor is the correct positioning of elements that constitute the mold and the plug. The lack of proper control in this step may lead to dimensional deviations in amounts exceeding tolerance levels. Addressing all these variables lead to an increase in global cost of the process, affecting line automation.
Thus, in light of the foregoing, the demand for solutions that relinquish the core-making phase on the casting of large-scale engines is noticeable, as to enable viability on industrial scale.